Capitalize the default Flight environment (#28402)

It's cleaner and more in line with how we style other badges like "Memo"
and "ForwardRef" in DevTools.

DiffTrain build for [4ea424e63d](https://github.com/facebook/react/commit/4ea424e63d1a74ce57ef675b64a8c4eabfdb2fdc)

compiled/facebook-www/REVISION

@@ -1 +1 @@
-fa2f82addc7c817892c482792f56a35277e8b75a
+4ea424e63d1a74ce57ef675b64a8c4eabfdb2fdc

compiled/facebook-www/ReactDOMTesting-prod.modern.js

@@ -17072,7 +17072,7 @@ Internals.Events = [
 var devToolsConfig$jscomp$inline_1783 = {
   findFiberByHostInstance: getClosestInstanceFromNode,
   bundleType: 0,
-  version: "18.3.0-www-modern-e933abb6",
+  version: "18.3.0-www-modern-89b07437",
   rendererPackageName: "react-dom"
 };
 var internals$jscomp$inline_2154 = {
@@ -17103,7 +17103,7 @@ var internals$jscomp$inline_2154 = {
   scheduleRoot: null,
   setRefreshHandler: null,
   getCurrentFiber: null,
-  reconcilerVersion: "18.3.0-www-modern-e933abb6"
+  reconcilerVersion: "18.3.0-www-modern-89b07437"
 };
 if ("undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__) {
   var hook$jscomp$inline_2155 = __REACT_DEVTOOLS_GLOBAL_HOOK__;
@@ -17524,4 +17524,4 @@ exports.useFormState = function (action, initialState, permalink) {
 exports.useFormStatus = function () {
   return ReactCurrentDispatcher$2.current.useHostTransitionStatus();
 };
-exports.version = "18.3.0-www-modern-e933abb6";
+exports.version = "18.3.0-www-modern-89b07437";

compiled/facebook-www/ReactFlightDOMServer-dev.modern.js

@@ -1172,7 +1172,7 @@ if (__DEV__) {
 
       {
         request.environmentName =
-          environmentName === undefined ? "server" : environmentName;
+          environmentName === undefined ? "Server" : environmentName;
       }
 
       var rootTask = createTask(request, model, null, false, abortSet);